1. Field of the Invention
The present invention relates to a power transfer device adapted for use in combination with a power transmission for a part-time four wheel drive vehicle to selectively transfer output drive torque of the power transmission to a pair of front road wheels and a pair of rear road wheels, and more particularly to a lubrication mechanism for an auxiliary change-speed mechanism in the power transfer device.
2. Description of the Prior Art
In U.S. Pat. No. 4,440,042 issued on Apr. 3, 1984, there has been proposed an auxiliary change-speed mechanism in the form of a helical planetary gear assembly which includes a housing, an input shaft rotatably mounted within the housing for drive connection to an output shaft of a power transmission, an output shaft arranged coaxially with the input shaft and rotatably mounted within the housing for rotation relative to the input shaft, a planetary gear unit having an input element mounted on the input shaft for rotation therewith and an output element connectable with the output shaft, and a collar of sleeve member axially slidably mounted on the output shaft and shiftable between a first position in which it effects a drive connection between the input and output shafts and a second position in which it effects a drive connection between the output element of the planetary gear unit and the output shaft.
In such a conventional auxiliary change-speed mechanism, it is required to forcibly supply a sufficient amount of lubricating oil to bearing and intermeshed portions of component parts of the change-speed mechanism without causing any increase in size of the power transfer device.